Electrostatic separator which utilizes electrodes with a shape of geometrically periodic delay lines



March 14, 1967 v 0 3,309,517

ELECTROSTATIC SEPARATOR WHICH UTILIZES ELECTRODES WITH A SHAPE OFGEOMETRICALLY PERIODIC DELAY LINES Filed Aug. 14, 1965 UUUUUUHUUUDINVENTOR :RLIOT BY 70ml who; I

United States Patent 3,309,517 ELECTRQSTATIC SEPARATOR WHICH UTILIZESELECTRODES WITH A SHAPE OF GEOMETRI- CALLY PERIODIC DELAY LINES RaymondLiot, 79 Blvd. Haussmann, Paris, France Filed Aug. 14, 1963, Ser.No.,302,101 Claims priority, application France, Sept. 4, 1962,

908,514 Claims. (Cl. 25041.9)

The present invention relates to improvements in electrostaticseparators for use with particle accelerators.

It is known that the beam of accelerated particles leaving anaccelerator, in particular, a beam of heavy particles is not in generalpure, that is, does not contain the particles of one and the same massand velocity, but contains mixed particles of different species andtypes, having a momentum substantially the same but of different masses,and, consequently, different velocities inversely proportional to themasses. If one desires, for a given research in physics, to have a purebeam, it is necessary to proceed with the separation of the particles ofdesired mass from those having other masses.

It is known to make this separation with the aid of electrostaticseparators, constituted in principle of a condenser between theelectrodes of which one causes to pass the beam from the output of theaccelerator, across the direct-current electric field establishedbetween these electrodes. The particles of different velocities followwithin this field different trajectories or paths and undergo adeviation or deflection of which the amplitude at the output of thecondenser is inversely proportional to the momentum and to the velocityof the particle, that is, with a constant quantity of momentum,inversely proportional only to the velocity. These different paths arethereupon intercepted by the utilization devices of the particles whichare desired or absorption devices for those which are not desired.

A transverse magnetic field, crossedwith the electric field, mayadditionally be established either across the space between theelectrodes of the condenser or across the space traversed by thetrajectories or paths of the particles ahead of and/or behind thecondenser, with a view to diminish the chromatic aberration and toincrease thus the reciprocal separation of the trajectories withoutoverlap, and in addition to disperse the paths or trajectories withdeviation in one or the other direction or even without deviation.

The same separators may also be utilized to extract the particles of agiven energy of a beam which, though pure from the point of view ofmass, is not mono-energetic,

that is, of which the particles of same mass leave the accelerator withvelocities distributed within a certain spectrum.

In order to obtain an efficient separation along a reduced path, it isnecessary to establish within the condenser an electric field which isas intense as possible, that is, to establish between the electrodes adifference of potential as high as possible.

A limitation in this approach is the appearance, beginning with acertain voltage, of sparkovers between the electrodes carried at thehigh voltage, sparkovers which, in the known prior art separators, arefollowed by steady arcs producing a short circuit with circuitinterruption of the high voltage supply source, and with the necessityto stop the experiments during the time of reapplying the voltage.

The object of the present invention is an electrostatic particleseparator in which this inconvenience is eliminated, that is, in whichthe sparkovers, to the extent to which they are still produced, remainintermittent without being followed by permanent arcs and do not add tothe 3,39%,517 Patented Mar. 14, 1967 substantial disturbance of theoperation of the installation.

The invention is based on a certain hypothesis of applicant herein asregards the mechanism of formation of these arcs; however, it must beunderstood that the present invention does not depend in any way on thevalidity of this hypothesis.

It is known that the occurrence of a spark between the electrodes of acondenser is a generator of an entire spectrum of high frequencies, andapplicant assumes that within the spectrum there is also always afrequency with respect to which the assembly of the two electrodes inquestion constitutes a bi-filar open line with high Q factor and alongwhich a very high amplitude of the wave will be produced therefore atthe frequency in question. It is this amplitude which therefore would beresponsible for entertaining the sparking and the transformation of anintermittent spark into a permanent arc.

To remedy this disadvantage, it is appropriate therefore to diminish theQ factor, and a possible means would consist in damping the circuit byconstituting or covering the electrodes with a material of poorconductivity, such as graphite, semi-conductors, resistant alloys, etc.

However, these means would be impractical, for such materials orcoatings would be damaged at more or less brief intervals by theintermittent sparks that subsist between the electrodes under highvoltage, thereby produc ing evaporation or discharge of gases disastrousfor the electrodes and adjoining parts.

The present invention therefore proposes other means consisting ingiving to these electrodes the structure of a delay line, known per sein the construction of microwave tubes.

According to one development of the present invention, resistances maybe introduced into the structure of such delay lines.

Accordingly, it is an object of the present invention to provide aparticle separator of the type mentioned hereinabove which effectivelyeliminates the shortcomings and disadvantages cited hereinabove andencountered with the prior art constructions.

Another object of the present invention resides in the provision of anelectrostatic separator for use in particle accelerators whicheliminates by simple means the danger of sparking and lasting arcing.

Still another object of the present invention resides in the provisionof an electrostatic separator for particle accelerators which assuresuninterrupted experiments without dangers of short circuits within theseparator.

A further object of the present invention resides in the provision of anelectrostatic particle separator, particularly for heavy particlesleaving an accelerator, which precludes the possibility of permanentarcs within the separator without danger of contamination to partsthereof by evaporation or discharge of harmful gases.

These and other objects, features and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawing which shows, forpurposes of illustration only, several embodiments in accordance withthe present invention, and wherein:

FIGURE 1 is a longitudinal cross-sectional view through a separatoraccording to the present invention within an accelerator installationindicated only schematically;

FIGURE 2 is a transverse cross-sectional view of the separator of FIGURE1, taken along line IIII of FIG- URE 1;

FIGURE 3 is a partial elevational view of a first embodiment of anelectrode structure of the separator according to the present invention;

FIGURE 4 is a partial elevational View of a second embodiment of anelectrode structure of the separator in accordance with the presentinvention;

FIGURE is a partial elevational view of a third embodiment of anelectrode structure of the separator according to the present invention;

FIGURE 6 is a partial transverse cross-sectional view through theelectrodes formed in accordance with the embodiment of FIGURE 3, with amodification according to a further development of the presentinvention; and

FIGURE 7 is a partial transverse cross-sectional view of an electrodeelement formed in accordance with the embodiments of FIGURES 4 or 5,with a further modification according to the present invention.

Referring now to the drawing, wherein like reference numerals are usedthroughout the various views to designate like parts, and moreparticularly to FIGURE 1, the rectangle 1 represents schematically aparticle accelerator of which the beam 2 enters into a particleseparator comprising, within a metallic cylinder 3 open at both sidesthereof, a pair of electrodes 4 and 5 carried respectively at the highpositive and negative voltage with respect to the grounded cylinder 3,and consequently forming the plates of a condenser.

As an illustrative example, it is assumed that the space between theelectrodes 4 and 5 is traversed by a transverse magnetic field furnishedby the pole pieces 6 and 7, shown in FIGURE 2, in such a direction thatthe Lorentz force exerted by this field on the particles in movementopposes the electric force exerted on these same particles by theelectric field due to the difference in the potential applied betweenthe electrodes 4 and 5. However, as known, the separator could functionalso without this magnetic field, or the magnetic field could beestablished to traverse the spaces between the output of the accelerator1 and the input of the cylinder 3 or after the output from the cylinder3. As is known, the beam 2 is divided within such separators into aplurality of trajectories such as 8, 9 and 10 dependent on the velocityof the particles which follow these trajectories; along the paths ofthese trajectories are disposed utilization or absorption devices 11,12, and 13 for the utilization of the particles which have the desiredvelocity or the absorption of the particles which are of no interest.

According to the present invention, the electrodes 4 and 5 of theseparation condenser have a delay line structure known in microwavetubes, for example, in the form of a ladder with plain bars or rungs(FIGURE 3) or cut rungs (FIGURE 4) or in the form of an interdigitalline (FIG- URE 5). Each of these forms comprises longitudinal supports14 and 15 to which are fixed respectively the bars or rungs 16 (FIGURE3) or the fingers 17 and 18 (FIG- URES 4 or 5).

According to a further development of the present invention, dampingresistances are interconnected within the bodies of the described oranalogous structures. To that effect, the delay line, for example, ofFIGURE 3 will be transformed by separating the bars or rungs 16 from thesupports 14 and 15 (FIGURE 6) and by shunting the intervals ofseparation by means of resistances 19. In an analogous manner, one willseparate, within each of the combs composing the lines according toFIGURES 4 and 5, the fingers 17 from the supports 14 or the fingers 18from the support 15, and one will then shunt the intervals of separationby resistances 19 as shown in FIG- URE 7.

The realizations described in a non-limitative manner as well as allother equivalent realizations utilizing the exposed principles, bringabout an important improvement to the operation of electrostaticparticle separators, which operation is only slightly disturbed by theintermittent sparkovers whereas the more or less permanent arcs whichwould necessitate shut-down times in the operation, are suppressed or atleast strongly reduced.

While I have shown and described several embodiments in accordance withthe present invention, it is understood that the same is not limitedthereto, but is susceptible of numerous changes and modifications asknown to a person skilled in the art, and I therefore do not wish to belimited to the details shown and described herein, but intend to coverall such changes and modifications as are encompassed by the scope ofthe appended claims.

I claim:

1. In a electrostatic separator for separating charged particlescontained in a particle beam said charged particles having individualmomentum values resulting from at least one different parameter of thetwo momentum parameters consisting of mass and velocity, respectively,of each particle, the improvement essentially consisting of:

a spaced pair of mutually facing electrodes with a shape 7 ofgeometrically periodic delay lines,

means for applying an electrostatic potential difference between saidelectrodes,

and means for directing the particle beam through the space between saidelectrodes.

2. In an electrostatic separator for separating charged particlescontained in a particle beam said charged particles having individualmomentum values resulting from at least one different parameter of thetwo momentum parameters consisting of mass and velocity, respectively,of each particle, the improvement essentially consisting of a spacedpair of mutually facing electrodes with a shape of geometricallyperiodic delay lines, at least one of said electrodes having the shapeof a ladder-type delay line including rungs substantially perpendicularto a pair of longitudinal bars,

means for applying an electrostatic potential difference between saidelectrodes,

and means for directing the particle beam through the space between saidelectrodes.

3. In an electrostatic separator for separating charged particlescontained in a particle beam said charged particles having individualmomentum values resulting from at least one different parameter of thetwo momentum parameters consisting of mass and velocity, respectively,of each particle, the improvement essentially consisting of:

a spaced pair of mutually facing electrodes with a shape I ofgeometrically periodic delay lines, at least one of said electrodeshaving the shape of a ladder-type delay line including rungssubstantially perpendicular to a pair of longitudinal bars, means forapplying an electrostatic potential difference between said electrodes,

and means for directing the particle beam through the space between saidelectrodes,

said rungs being cut substantially in the plane of longi tudinalsymmetry of the delay line to separate the ladder into a pair ofmutually facing comb-type structures. p 4. In an electrostatic separatorfor separating charged particles contained in a particle beam saidcharged particles having individual momentum values resulting from atleast one different parameter of the two momentum parameters consistingof mass and velocity, respectively, of each particle, the improvementessentially consisting of:

a spaced pair of mutually facing delay line electrode structures atleast one of said electrode structures having the shape of aninterdigital delay line,

means for applying an electrostatic potential difference between saidelectrodes,

and means for directing the particle beam through the space between saidelectrodes.

5. In an electrostatic separator for separating charged particlescontained in a particle beam said charged particles having individualmomentum values resulting from at least one dilferent parameter of thetwo momentum parameters consisting of mass and velocity, respectively,of each particle, the improvement essentially consisting of:

a spacedpair of mutually facing delay line electrode structures at leastone of said electrode structures being composed of a pair of comb-likestructures provided with fingers substantially perpendicular to alongitudinal bar,

means for applying an electrostatic potential difference between saidelectrodes,

and means for directing the particle beam through the space between saidelectrodes.

6. An electrostatic separator for separating charged particles containedin a particle beam said charged particles having individual momentumvalues resulting from at least one different parameter of the twomomentum parameters consisting of mass and velocity, respectively, ofeach particle, said separator comprising:

a spaced pair of mutually facing delay line electrode structures atleast one of said electrode structures being composed of a pair ofcomb-like structures, provided with fingers substantially perpendicularto a longitudinal bar,

means for applying an electrostatic potential difference between saidelectrodes,

and means for directing the particle beam through the space between saidelectrodes,

said fingers being mechanically separated from the bar to provide spacesbetween said fingers and said bar, and resistive means connected acrosssaid last mentioned spaces.

7. An electrostatic separator charged particles contained in a particlebeam said charged particles having individual momentum values resultingfrom at least one different parameter of the two momentum parametersconsisting of mass and velocity, respectively, of each particle, saidseparator comprising:

a spaced pair of mutually facing electrodes with a shape ofgeometrically periodic delay lines,

at least one of said electrodes having the shape of a ladder-type delayline including rungs substantially perpendicular to a pair oflongitudinal bars,

means for applying an electrostatic potential difference between saidelectrodes,

and means for directing the particle beam through the space between saidelectrodes,

said rungs being mechanically separated from said bars to provide spacesbetween said rungs and said bars, and resistive means connected acrosssaid last mentioned spaces.

8. In an electrostatic separator for charged particles contained withina particle beam said charged particles having individual momentum valuesas a result of at least one different parameter of the two momentumparameters consisting of mass and velocity, respectively, of eachparticle, including electrode means operable to establish a transverseelectrostatic field upon application of a high potential differencebetween the electrode means to separate out the particles according tothe momentum values thereof as they pass through said electrostaticfield,

the improvement essentially consisting of means for preventing theestablishment of permanent arcs across said electrode means by loweringthe Q factor of said electrode means for a given frequency, within thefrequency spectrum of a transient sparkover between said electrodemeans,

said means including a plurality of mutually facing spaced electrodeswith a shape of geometric periodic delay lines.

9. In an electrostatic separator for charged particles contained withina particle beam said charged particles having individual momentum valuesas a result of at least one difierent parameter of the two momentumparameters consisting of mass and velocity, respectively, of eachparticle, including electrode means operable to establish a transverseelectrostatic field upon application of a high potential differencebetween the electrode means to separate out the particles according tothe momentum values thereof as they pass through said electrostaticfield,

the improvement essentially consisting of means for preventing theestablishment of permanent arcs across said electrode means by loweringthe Q factor of said electrode means for a given frequency within thefrequency spectrum of a transient sparkover between said electrodemeans,

said means including spaced delay line circuit means having a pluralityof delay circuit elements and damping means connected across adjacentelements of said delay circuit means.

10. In an electrostatic separator for charged particles contained withina particle beam said charged particles having individual momentum valuesas a result of at least one different parameter of the two momentumparameters consisting of mass and velocity, respectively, of eachparticle, including electrode means operable to establish a transverseelectrostatic field upon application of a high potential differencebetween the electrode means to separate out the particles according tothe momentum values thereof as they pass through said electrostaticfield,

the improvement essentially consisting of means for preventing theestablishment of permanent arcs across said electrode means by loweringthe Q factor of said electrode means for a given frequency within thefrequency spectrum of a transient sparkover between said electrodemeans,

said means including a spaced pair of mutually facing electrodes with ashape of geometrically periodic delay lines.

References Cited by the Examiner UNITED STATES PATENTS 2,779,006 1/ 1957Albersheim 333-81 2,868,986 1/1959 Lanneau et al. 25041.9 2,915,71512/1959 Young 33381 2,942,142 6/1960 Dench 315-3.5 3,016,458 1/1962Blewett 250-41.9 3,093,733 6/1963 Blewett et al. 250-41.9

RALPH G. NILSON, Primary Examiner.

W. F. LINDQUIST, Assistant Examiner.

1. IN A ELECTROSTATIC SEPARATOR FOR SEPARATING CHARGED PARTICLESCONTAINED IN A PARTICLE BEAM SAID CHARGED PARTICLES HAVING INDIVIDUALMOMENTUM VALUES RESULTING FROM AT LEAST ONE DIFFERENT PARAMETER OF THETWO MOMEMENTUM PARAMETERS CONSISTING OF MASS AND VELOCITY, RESPECTIVE,OF EACH PARTICLE, THE IMPROVEMENT ESSENTIALLY CONSISTING OF: A SPACEDPAIR OF MUTUALLY FACING ELECTRODES WITH A SHAPE OF GEOMETRICALLYPERIODIC DELAY LINES, MEANS FOR APPLYING AN ELECTROSTATIC POTENTIALDIFFERENCE BETWEEN SAID ELECTRODES, AND MEANS FOR DIRECTING THE PARTICLEBEAM THROUGH THE SPACE BETWEEN SAID ELECTRODES.